THE RELEASE of Biohazard's "Uncivilization" was going to be an all-day celebration, according to singer-bassist Evan Seinfeld. An album signing and performance at Vintage Vinyl in Woodbridge, N.J., was to be followed by a huge private party "with my whole walk-of-life friends, my hipster friends, my biker buddies, my model-actor-scenester friends -- a super trendy New York joint."

"Instead, we spent the day sitting on our rooftops."

The release date was Sept. 11.

That fateful September morning found Seinfeld asleep in his Astoria apartment, two blocks from the East River.

"I had just broken up with my girlfriend, but she came over and woke me up," Seinfeld recalls. "She turned on the TV and said 'Look!' I jumped out the window and went up the fire escape to the roof and saw the second plane hit live."

On the day that New York skyline changed forever, Seinfeld first tried to contact people he knew who worked in the World Trade Center buildings. "We all lost people who were close to us," he says, including firemen and policemen called to ground zero, "but we also knew people who got out of the building and are still real shellshocked right now."

While the "Uncivilization" parties were canceled, Seinfeld was left wondering about the unsettling irony that an album full of songs about societal violence and man's inhumanity to man was released on a day that seemed to underscore those very themes.

According to Seinfeld, "We're a band that's socially active and politically relevant, looking at our dysfunction as a nation, identifying and trying to turn a flashlight on our dark secrets, whether it be our foreign policies or our problems with ourselves." Which made for indelicate timing on some of the album's lyrics, notably "Unified," which includes this line: "I want to blow up the White House and the shopping malls."

"I felt horrible that people who didn't know about the band were going to read that and take it literally and think we're subversives," Seinfeld admits. But, he adds, "anybody who has followed Biohazard would know that's a radical metaphor for changing the system and our consumer-oriented society and would not take it out of context.

"We love America, we're so proud of where we're from," Seinfeld says. "We use our music as therapy, to release our negative energy in a positive way. Sure, we love to bring up society's ills, but we try to find remedies and raise social consciousness among the youth who buy our records, come to our concerts and tattoo our logos on their bodies. And as much as we talk about the problems, there's nowhere else in the world I'd want to live."

Biohazard was slated to start a European tour with Slayer on Sept. 13, but it ended up being delayed when all international flights were temporarily grounded. After playing a Red Cross benefit in Boston, the band was on one of the earliest flights out of the country because, Seinfeld explains, "unlike a lot of American bands that canceled their overseas tours, we felt that the best thing we could do was not bow down to terrorism."

As the "Tattoo the Earth" tour wound through a dozen European countries in 35 days, Seinfeld noted "a huge sympathy from the crowds, a sense of a one-world nation and humanity. We did a song called 'Loss' from our second album [1992's "Urban Discipline"], written for all of our friends who died growing up in Brooklyn, where there was a lot of violence, a lot of drugs, gang warfare and guns. I never thought it would apply to thousands who died at one time, but it seemed so applicable and so poignant that we started doing it as an acoustic ballad and every night people were lighting lighters. We had a moment of silence and it was very spiritual. I felt like we were uniting people."

In a sense, that's what Biohazard intended from the start.

"We're not a political band, we're a social band, a band of the people," Seinfeld says. "We sing about our own true life, not about abstract politics, but about how things in life affect us. We're a soundtrack for angry youth who want to make a change for the better."

That soundtrack has been loud, fast, abrasive, raging against the sociopolitical machine with bruising intensity. The band's name and the attendant symbol tattooed on Seinfeld's body were taken from a lab safety supply catalogue. "It means 'dangerous to life,' which was everything we were growing up with in Brooklyn -- gangs, drugs, violence, racism, close-mindedness, AIDS and social diseases in general. It completely symbolized everything that we stand against."

Biohazard was one of the first bands to fuse its dominant hardcore and metal sounds with rap. It's a hip and commercially viable formula these days, and Biohazard is acknowledged as part of its godfather pool. But according to Seinfeld, it was a different story in the late '80s, when there was little crossover between black and white urban sounds.

"The bands now that emulate nu-metal and rap-metal come from white suburbia, and I'm sure they love hip-hop and feel the music, but they couldn't possibly relate the way we did as kids in multi-ethnic Brooklyn. Rap was rhythmic and realistic, and the lyrics were right up our alley. We understood every word of it."

Seinfeld remembers being ostracized by the hardcore and metal communities. "They didn't want to have anything to do with us. 'You guys got some great riffs and a heavy sound but what's with the rapping? You guys shouldn't be rapping!' As for the rap community, we got some respect, but the general comments were, 'You guys play great kill-your-father, kill-your-mother rock 'n' roll.' It was really racially segregated: Rap was black music and rock was white music, and where it crossed over was a tiny area."

The commonality of urban experience did eventually make for some intriguing collaborations after Run-DMC built the rap-rock bridge in 1986 by teaming up with Aerosmith on "Walk This Way." Biohazard walked across it in 1993 to meet up with Queens' hardcore rap trio, Onyx, first on a remix of Onyx's "Slam" by bassist Billy Graziadei, followed by the title track from "Judgment Night." That double-platinum soundtrack featured a slew of rock-rap collaborations, including Pearl Jam with Cypress Hill, Mudhoney with Sir Mix-A-Lot, Teenage Fanclub with De La Soul and Slayer with Ice-T.

These days, Ice-T is playing a cop on "Law & Order: Special Victims Unit," and Seinfeld is playing a convict on HBO's "Oz." As tattooed biker Jaz Hoyt, he's had some memorable conflicts with resident Aryan supremacist Vern Schillinger (actor J.K. Simmons, who plays a police psychiatrist on "Law & Order: SVU"). Seinfeld was already a fan of the gritty prison drama when the opportunity to join its cast arose.

"Next thing I know, I'm in [producer-director] Tom Fontana's office having a conversation about my hypothetical character on the show. The next day, he messengers a script to my house, on a Friday with a call time for Monday morning. I told everybody I had an audition, a screen test -- I was very excited. I show up Monday morning at 6:30 a.m. in Chelsea [the "Oz" set location], and suddenly I'm on the show -- no rehearsals, no nothing. He threw me right into the fire. They told me, 'Whatever you do, don't study acting. We want you because you're real.' "

That was three years and 30 episodes ago. The eight-episode fifth season kicks off Sunday and, Seinfeld promises, "this is going to be one of the best."

"I still have a really, really long way to go," he says of his acting skills. "I watch my early stuff and I wince and cringe. Unlike music, where you sing and it's either on key or off key, there are degrees of getting it right [with acting]. Sometimes you convince a few people, sometimes you convince a lot of people. I got challenged a lot more as an actor this year and it's something that I'm really looking forward to in the future."

And just how long will Jaz Hoyt survive on a series that has killed off 49 characters in its first four seasons?

Seinfeld's not telling, though he hopes to continue parallel music and acting careers. And if Seinfeld ever gets to star in his own television show, it should be easy to come up with a catchy title for it.

BIOHAZARD -- Appearing Friday at the 9:30 club with Clutch and Primer 55. * To hear a free SoundBite from Biohazard, call Post-Haste at 202/334-9000 and press 8101. (Prince William residents, call 703/690-4110.)

Biohazard's "Uncivilization" contains timely and unsettling imagery. Evan Seinfeld is at center.